importing G klass and OBD2

In February of last year I imported a G500 from Europe. I did a lot of research and went with RI close to me. The car is sitting there ever since. I thought that "conversion" (side marker lights and testing) would take some time but not 4 month! I being told that since my G does not have OBD2 the process is even more expensive and much longer. I am really puzzled. Does any one know if OBD2 (on board diagnostics) is mandatory in all 50 states? Does any one know how much the OBD2 (sensors, wiring, etc.)might cost with and without installation? I have brabus engine kit (sport camshafts and special valve springs)and exhaust installed, will any of this crap affect the performance? Thanx in anticipation, any comment would be greatly appreciated.

PS. Greed sux